I'd like to hear more...between the light use my UL will get, and adding Mystery oil most of the time and lead additve some of the time, I'm not too concerned...but it does sound like a reasonable upgrade.

I fail to see the need for hardened valve seats on "normal" 45's. My advice on the subject came from Fred Warr who knows a thing or two about 'em; he reckoned that since flatheads burn oil by design, the standard trick of dropping the throttle on a run to bring oil up the bores gave the engine as much "fuel additive" as you'd ever need to compensate for the missing lead halides.

I sent my 72 Ironhead for a top-end strip and refurb some years ago, it had about 35K miles on it then and had never been rebuilt. This after about 3 years of running solely unleaded fuel; the engineer reported back that there were no signs of valve seat recession, and I used that thing pretty hard!

Hi. I have had hardened seats in my BTSV for many years now. Never regretted this. I am positive that this extends the live of valves and seats. And it brings new life to sylinders with valve seats that is ground many times.